On the basis of cost per unit of energy obtained by combustion, coal is generally less expensive than petroleum. Two approaches are presently employed for conversion of coal to synthetic petroleum that may then be used as feed stocks for manufacturing fuels and chemicals similar to those made from conventional petroleum.
One principal processing approach is called “direct liquefaction” that includes: 1. gasification of part of the coal by partial combustion to produce a gaseous product containing both hydrogen and carbon monoxide (syngas): 2. changing the composition of the gas stream to substantially all hydrogen by reacting the carbon monoxide with water to produce both additional hydrogen and carbon dioxide with removal of the carbon dioxide; and 3. chemical reaction of the hydrogen stream thus formed with the remaining coal at a suitable combination of temperature and pressure in the presence of a catalyst and a hydrogen transfer liquid, to transform the coal to synthetic petroleum (liquefaction).
The principal processing steps in the approach called “indirect liquefaction” include: 1. gasification of all of the coal by partial combustion to produce a gaseous product containing both hydrogen and carbon monoxide (syngas); 2. adjusting the hydrogen content of the gas by reacting part of the carbon monoxide with water to produce both hydrogen and carbon dioxide with removal of the carbon dioxide, to produce a stream containing a preferred composition of hydrogen and carbon monoxide; and 3. reacting the hydrogen and carbon monoxide at a suitable combination of temperature and pressure in the presence of a catalyst to make paraffinic hydrocarbons (liquefaction). This reaction is widely known as the “Fischer-Tropsch” synthesis and the products provide suitable feed stocks for many fuel and chemical production processes. However the Fischer-Tropsch products are deficient in hydrocarbons with cyclic chemical structures including aromatics (e.g. toluene) or cycloaliphatics (e.g. cyclohexane).
Both of these conventional processes use the reaction of carbon monoxide with water, widely known as the “water gas shift reaction” or “WGSR” as a significant and separate processing step to adjust the composition of the reacting gas stream to a preferred composition. That WGSR may be summarized as follows:CO+H2O→CO2+H2 The water gas shift reaction noted above, which is utilized to adjust the ratio of H2 to CO in the syngas to provide an optimal ratio for downstream processing, is, as noted, typically carried-out in a separate stand-alone reactor. This then eventually provides a suitable feed for the coal liquefaction reactor. The present invention is, among other things, directed at elimination of this separate reactor for the WGSR and improvement of the overall processes economics, along with the application of such process to all types of coal and the formation of products that also include cyclic organic compounds that may be particularly preferred for selected fuels and other chemical manufacturing requirements.